The purpose of this study is to verify the mediating effect of social media use motives in the gender difference in social media addiction. To this end, the Bergen Social Media Addiction Scale and the Social Media Use Motives Scale–Revised were administered to 433 college students (154 males and 279 females) who use social media. The results of the study showed that coping motives, pastime motives, expression motives, and concealment motives functioned as mediating variables in the gender difference in social media addiction. Among these four motives, the mediating effect of coping motives showed the largest effect size. These research results suggest that when intervening in social media addiction among female college students, interventions should focus on coping motives, pastime motives, expression motives, and concealment motives.